End-Triassic mass extinction and CAMP

Advances in the study of the end-Triassic mass extinction

The U-Pb and Ar-Ar dataset underpinning the calibration of the Triassic time scale was critically reviewed by József Pálfy and his collaborators, revealing some of the weaknesses of the currently used time scales and suggesting ways to achieve better precision and accuracy. The Late Triassic, and the Norian Stage in particular, was shown to have a significantly longer duration than previously estimated. This requires recalculation of evolutionary rates for the interval preceding the end-Triassic mass extinction.

Advances have been made in the study of the end-Triassic extinction and Early Jurassic radiation. The characteristic negative carbon isotope anomaly has not been observed in carbonate platform deposits in a surface section (Kőris Hill), nor in boreholes (Zt-62, Süt-28). A likely cause is submarine erosion, possibly related to the biocalcification crisis at the Triassic-Jurassic boundary, which prevented either the carbonate precipitation and deposition or the preservation of sediment. The system boundary is accurately drawn on the basis of calcareous algae and foraminifers, but the duration of the gap remains unknown. We attempted to prove the „super-greenhouse” warming, postulated for the end-Triassic, by measuring the oxygen isotope composition of radiolarians in the Kunga Island boundary section in Canada. However, the obtained results are ambiguous due to the secondary diagenetic overprint of the siliceous tests.

The latest results of Jurassic time scale research, which provides a temporal framework for biotic evolution, was summarized in a review article. Palynological studies demonstrated peak abundance of fern spores and marine prasinophyte algae at the Triassic-Jurassic boundary. These changes are coeval with the previously documented carbon isotope excursion and indicate a synchronous crisis that affected plants of both the terrestrial and marine biotas. Coeval sedimentary sequences from drillcores in the Mecsek Mts. record cyclic changes in the vegetation.

The end-Triassic extinction and CAMP

A major perturbation of marine and terrestrial ecosystems is interpreted to be linked to the volcanic activity of the Central Atlantic Magmatic Province (CAMP) volcanism. Traces of volcanic activity, the trigger of the end-Triassic extinction, have been identified in a marine Triassic-Jurassic boundary section at Csővár, Hungary. The studied section represents a continuous key marine section of the NW Tethyan realm. Analysis of clay minerals helped characterize the concomitant climate and environmental change. During phases of high volcanic activity, the release of sulfur (mostly SO2 and some H2S) may cause short-term cooling and a regional acidification of terrestrial ecosystems through the formation of sulfuric acid (H2SO4) rain. The scientists propose this signal as a potentially powerful correlation tool for short-term changes at the Triassic/Jurassic boundary of the NW Tethyan realm and adjacent areas.